Reciprocating piston engines in which a cylinder bore in a cylinder block is line with a liner are known in the field. For example, WO 2014/006199 A2 discloses a cylinder liner composed of gray cast iron for casting into an engine block of an internal combustion engine, in which a means for reinforcing the connection of the cylinder liner to the casting material of the engine block is arranged at least in regions on an outer circumferential surface of the cylinder liner, the means being a wire mesh or wire grating that does not melt or open while the engine block is cast, wherein the means is welded to the cylinder liner in at least one region.
The present disclosure provides an improved reciprocating piston engine and a motor vehicle with such a reciprocating engine. One example includes a reciprocating piston engine which has a cylinder block, at least one combustion chamber arranged in the cylinder block, and a liner which borders the combustion chamber and is composed of a first material, wherein the reciprocating piston engine comprises a reinforcing element composed of a second material for the radial reinforcement of the liner, said reinforcing element being arranged between the cylinder block and the liner and at least partially surrounding the liner, with the second material having a higher modulus of elasticity than the first material.
According to the present disclosure, an arrangement which imparts greater rigidity to the at least one liner is provided. The liner may then therefore, be better protected against bore distortion which may arise at the upper end of the liner during operation of the reciprocating piston engine because of combustion pressures and high temperatures, in particular in the case of open deck designs. A smaller bore distortion may permit the use of piston rings having a lower pretension, and therefore, the friction between the piston ring and the liner may be reduced. Greater efficiency of the reciprocating piston engine may therefore be achieved. An increased efficiency may further lead to preserving fuel and may reduce CO2 emission by the engine.
Other attempts to address negative impacts on bore distortion due to higher movement distances of the liners in an “open deck” reciprocating engine include the incorporation a metal matrix composite (MMC) closely fitted onto the outer periphery of the cylinder liner. One example approach is shown by Takami et al. in WO 2008/059330. Therein, an open-deck cylinder block with a cylinder liner incorporating a metal matrix composite ring is closely fitted onto an outer periphery of the cylinder liner and the MMC ring faces the top deck. Further, the liner material has a higher strength relative to that of the cylinder block material.
However, the inventors herein have recognized potential issues with such systems. As one example, MMC materials are typically higher cost relative to other common materials such as steel and MMC materials may further require complex fabrication methods for fiber-reinforced systems. As a further example, for degassing and manufacturing reasons, many cylinder blocks of internal combustion engines have an open deck design. The term “open deck” as used herein refers to an engine in which the top of the cylinder liners is not directly connected to the outer walls of the cylinder block. The open deck designs however may have a negative impact on bore distortion however because of the higher movement distances of the liners. For low friction between liner and piston, a low bore distortion may be required. For this reason, the high bore distortion may have a substantial impact on fuel economy. This may become more and more significant for high loaded turbocharged engines.
In one example, the issues described above may be addressed by a reciprocating piston engine which has a cylinder block, at least one combustion chamber arranged in the cylinder block, and a liner which borders the combustion chamber and is composed of a first material, wherein the reciprocating piston engine comprises a reinforcing element composed of a second material for the radial reinforcement of the liner, said reinforcing element being arranged between the cylinder block and the liner and at least partially surrounding the liner, with the second material having a higher modulus of elasticity than the first material. In this way, the degassing benefits of the open deck cylinder block may be combined with the structural rigidity and stiffness of the liners disposed between the cylinder and the engine block.
As one example of the disclosed reciprocating piston engine, the liner described may be composed of gray cast iron or aluminum and the reinforcing element may be composed of steel. It will be appreciated that as used herein, aluminum may refer also to aluminum alloys. Steel has a higher coefficient of elasticity when compared to gray cast iron or aluminum, and therefore, steel has a relatively high material rigidity. The liner in this case may be composed of the customary materials which have proven successful in regard to installation and operating properties.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.